content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.observable.subjects;
  
  import java.util.Arrays;
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.common.*;
  import io.reactivex.common.annotations.CheckReturnValue;
  import io.reactivex.observable.Observer;
  import io.reactivex.observable.internal.observers.DeferredScalarDisposable;
  
  /**
   * An Subject that emits the very last value followed by a completion event or the received error to Observers.
   *
   * <p>The implementation of onXXX methods are technically thread-safe but non-serialized calls
   * to them may lead to undefined state in the currently subscribed Observers.
   *
   * @param <T> the value type
   */
  
  public final class AsyncSubject<T> extends Subject<T> {
  
      @SuppressWarnings("rawtypes")
      static final AsyncDisposable[] EMPTY = new AsyncDisposable[0];
  
      @SuppressWarnings("rawtypes")
      static final AsyncDisposable[] TERMINATED = new AsyncDisposable[0];
  
      final AtomicReference<AsyncDisposable<T>[]> subscribers;
  
      /** Write before updating subscribers, read after reading subscribers as TERMINATED. */
      Throwable error;
  
      /** Write before updating subscribers, read after reading subscribers as TERMINATED. */
      T value;
  
      /**
       * Creates a new AsyncProcessor.
       * @param <T> the value type to be received and emitted
       * @return the new AsyncProcessor instance
       */
      @CheckReturnValue
      public static <T> AsyncSubject<T> create() {
          return new AsyncSubject<T>();
      }
  
      /**
       * Constructs an AsyncSubject.
       * @since 2.0
       */
      @SuppressWarnings("unchecked")
      AsyncSubject() {
          this.subscribers = new AtomicReference<AsyncDisposable<T>[]>(EMPTY);
      }
  
      @Override
      public void onSubscribe(Disposable s) {
          if (subscribers.get() == TERMINATED) {
              s.dispose();
          }
      }
  
      @Override
      public void onNext(T t) {
          if (subscribers.get() == TERMINATED) {
              return;
          }
          if (t == null) {
              nullOnNext();
              return;
          }
          value = t;
      }
  
      @SuppressWarnings("unchecked")
      void nullOnNext() {
          value = null;
          Throwable ex = new NullPointerException("onNext called with null. Null values are generally not allowed in 2.x operators and sources.");
          error = ex;
          for (AsyncDisposable<T> as : subscribers.getAndSet(TERMINATED)) {
              as.onError(ex);
          }
      }
  
      @SuppressWarnings("unchecked")
      @Override
      public void onError(Throwable t) {
          if (t == null) {
              t = new NullPointerException("onError called with null. Null values are generally not allowed in 2.x operators and sources.");
          }
          if (subscribers.get() == TERMINATED) {
              RxJavaCommonPlugins.onError(t);
              return;
          }
          value = null;
          error = t;
          for (AsyncDisposable<T> as : subscribers.getAndSet(TERMINATED)) {
              as.onError(t);
          }
      }
  
      @SuppressWarnings("unchecked")
      @Override
      public void onComplete() {
          if (subscribers.get() == TERMINATED) {
              return;
          }
          T v = value;
          AsyncDisposable<T>[] array = subscribers.getAndSet(TERMINATED);
          if (v == null) {
              for (AsyncDisposable<T> as : array) {
                  as.onComplete();
              }
          } else {
              for (AsyncDisposable<T> as : array) {
                  as.complete(v);
              }
          }
      }
  
      @Override
      public boolean hasObservers() {
          return subscribers.get().length != 0;
      }
  
      @Override
      public boolean hasThrowable() {
          return subscribers.get() == TERMINATED && error != null;
      }
  
      @Override
      public boolean hasComplete() {
          return subscribers.get() == TERMINATED && error == null;
      }
  
      @Override
      public Throwable getThrowable() {
          return subscribers.get() == TERMINATED ? error : null;
      }
  
      @Override
      protected void subscribeActual(Observer<? super T> s) {
          AsyncDisposable<T> as = new AsyncDisposable<T>(s, this);
          s.onSubscribe(as);
          if (add(as)) {
              if (as.isDisposed()) {
                  remove(as);
              }
          } else {
              Throwable ex = error;
              if (ex != null) {
                  s.onError(ex);
              } else {
                  T v = value;
                  if (v != null) {
                      as.complete(v);
                  } else {
                      as.onComplete();
                  }
              }
          }
      }
  
      /**
       * Tries to add the given subscriber to the subscribers array atomically
       * or returns false if the subject has terminated.
       * @param ps the subscriber to add
       * @return true if successful, false if the subject has terminated
       */
      boolean add(AsyncDisposable<T> ps) {
          for (;;) {
              AsyncDisposable<T>[] a = subscribers.get();
              if (a == TERMINATED) {
                  return false;
              }
  
              int n = a.length;
              @SuppressWarnings("unchecked")
              AsyncDisposable<T>[] b = new AsyncDisposable[n + 1];
              System.arraycopy(a, 0, b, 0, n);
              b[n] = ps;
  
              if (subscribers.compareAndSet(a, b)) {
                  return true;
              }
          }
      }
  
      /**
       * Atomically removes the given subscriber if it is subscribed to the subject.
       * @param ps the subject to remove
       */
      @SuppressWarnings("unchecked")
      void remove(AsyncDisposable<T> ps) {
          for (;;) {
              AsyncDisposable<T>[] a = subscribers.get();
              int n = a.length;
              if (n == 0) {
                  return;
              }
  
              int j = -1;
              for (int i = 0; i < n; i++) {
                  if (a[i] == ps) {
                      j = i;
                      break;
                  }
              }
  
              if (j < 0) {
                  return;
              }
  
              AsyncDisposable<T>[] b;
  
              if (n == 1) {
                  b = EMPTY;
              } else {
                  b = new AsyncDisposable[n - 1];
                  System.arraycopy(a, 0, b, 0, j);
                  System.arraycopy(a, j + 1, b, j, n - j - 1);
              }
              if (subscribers.compareAndSet(a, b)) {
                  return;
              }
          }
      }
  
      /**
       * Returns true if the subject has any value.
       * <p>The method is thread-safe.
       * @return true if the subject has any value
       */
      public boolean hasValue() {
          return subscribers.get() == TERMINATED && value != null;
      }
  
      /**
       * Returns a single value the Subject currently has or null if no such value exists.
       * <p>The method is thread-safe.
       * @return a single value the Subject currently has or null if no such value exists
       */
      public T getValue() {
          return subscribers.get() == TERMINATED ? value : null;
      }
  
      /**
       * Returns an Object array containing snapshot all values of the Subject.
       * <p>The method is thread-safe.
       * @return the array containing the snapshot of all values of the Subject
       */
      public Object[] getValues() {
          T v = getValue();
          return v != null ? new Object[] { v } : new Object[0];
      }
  
      /**
       * Returns a typed array containing a snapshot of all values of the Subject.
       * <p>The method follows the conventions of Collection.toArray by setting the array element
       * after the last value to null (if the capacity permits).
       * <p>The method is thread-safe.
       * @param array the target array to copy values into if it fits
       * @return the given array if the values fit into it or a new array containing all values
       */
      public T[] getValues(T[] array) {
          T v = getValue();
          if (v == null) {
              if (array.length != 0) {
                  array[0] = null;
              }
              return array;
          }
          if (array.length == 0) {
              array = Arrays.copyOf(array, 1);
          }
          array[0] = v;
          if (array.length != 1) {
              array[1] = null;
          }
          return array;
      }
  
      static final class AsyncDisposable<T> extends DeferredScalarDisposable<T> {
          private static final long serialVersionUID = 5629876084736248016L;
  
          final AsyncSubject<T> parent;
  
          AsyncDisposable(Observer<? super T> actual, AsyncSubject<T> parent) {
              super(actual);
              this.parent = parent;
          }
  
          @Override
          public void dispose() {
              if (super.tryDispose()) {
                  parent.remove(this);
              }
          }
  
          void onComplete() {
              if (!isDisposed()) {
                  actual.onComplete();
              }
          }
  
          void onError(Throwable t) {
              if (isDisposed()) {
                  RxJavaCommonPlugins.onError(t);
              } else {
                  actual.onError(t);
              }
          }
      }
  }
  